Given the mileage and the work you are doing already, I'd certainly think about doing the chains and guides. To dry the bolt holes I push the corner of a rag into the holes with a screwdriver. Just keep at it till you stop seeing light relecting back from the bottom of the hole. To clean the threads cut a groove at 90 degrees to the thread on an old bolt and work it in the bolt hole. The groove will pick up all the crap. Putting the head on is probably a 2 man job. I'd put a couple of thin battons across the top of the gasket and lower the head onto them. That way you dont catch an open valve on the block and you can wiggle the head about to line it up with the dowels. When you are happy its lined up just lift each end and remove the batons. Imagine you oil the new bolts on the M30 too? I prefer to use machine oil. I just put a little 'run' down each thread then leave them for a while. The worst runs off and you end up with just a film-you dont want oil under your new boltsHTH